Method and apparatus for transmitting control information in wireless communication system

ABSTRACT

A 5 th  Generation (5G) or pre-5G communication system for supporting higher data transmission rates beyond 4 th  Generation (4G) communication systems such as long term evolution (LTE) systems. A method for transmitting download control information in a communication system is provided. The method includes configuring the control information indicating at least one control channel element (CCE) including at least one resource element group (REG) unit interleaved based on the interleaving information indicated by a higher layer signaling; and transmitting, to a user equipment (UE), the configured control information.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/130,323, filed on Sep. 13, 2018, which has issued as U.S. Pat.No. 10,924,215 on Feb. 16, 2021 and is based on and claims priorityunder 35 U.S.C. § 119(a) of a Korean patent application number10-2017-0118982, filed on Sep. 15, 2017, in the Korean IntellectualProperty Office, and is based on and claims priority under 35 U.S.C. §119(a) of a Korean patent application number 10-2017-0126485, filed onSep. 28, 2017, in the Korean Intellectual Property Office, thedisclosure of which is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to wireless communication systems. Moreparticularly, the disclosure relates to methods and apparatuses fortransmitting download control channels.

2. Description of Related Art

In order to meet the demand for wireless data traffic soring since the4th generation (4G) communication system came to the market, there areongoing efforts to develop enhanced 5th generation (5G) communicationsystems or pre-5G communication systems. For the reasons, the 5Gcommunication system or pre-5G communication system is called the beyond4G network communication system or post long term evolution (LTE)system.

For higher data transmit rates, 5G communication systems are consideredto be implemented on ultra high frequency bands millimeter wave(mmWave), such as, e.g., 60 GHz. To mitigate pathloss on the ultra highfrequency band and increase the reach of radio waves, the followingtechniques are taken into account for the 5G communication system:beamforming, massive multi-input multi-output (MIMO), full dimensionalMIMO (FD-MIMO), array antenna, analog beamforming, and large scaleantenna.

Also being developed are various technologies for the 5G communicationsystem to have an enhanced network, such as evolved or advanced smallcell, cloud radio access network (cloud RAN), ultra-dense network,device-to-device (D2D) communication, wireless backhaul, moving network,cooperative communication, coordinated multi-point (CoMP), andinterference cancellation.

There are also other various schemes under development for the 5G systemincluding, e.g., hybrid FSK and QAM modulation (FQAM) and sliding windowsuperposition coding (SWSC), which are advanced coding modulation (ACM)schemes, and filter bank multi-carrier (FBMC), non-orthogonal multipleaccess (NOMA) and sparse code multiple access (SCMA), which are advancedaccess schemes.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providean apparatus and method for transmitting download control information ina communication system.

According to the disclosure, 5^(th) Generation (5G) wirelesscommunication systems support methods for transmitting download controlchannels, particularly distributed or interleaving transmission methodsand localized or non-interleaving transmission methods. Distributedtransmission methods may adopt interleaver or distributed mapping tomaximize frequency-axis diversity. The resource distribution for aparticular download control channel may be carried out in resourceelement group (REG) bundle size. At this time, one or more controlresource sets (CORESETs) may be set in the system bandwidth, and controlregions set with different system parameters may be configured tooverlap on the same time/frequency resource. In this case, in theoverlapping resource regions, the control channel distribution methodfor one control region may influence the transmission of the downloadcontrol channel in another control region, and thus, an efficient designis needed given the trade-off between the blocking probability anddiversity.

According to the disclosure, minimizing power consumption due to theuser equipment (UE)'s blind decoding is very critical in designing thesearch space of the 5G download control channel. To that end, upon blinddecoding each control channel candidate, it may be considered to reusethe channel estimation value used for prior decoding. For that purpose,the search space may be designed so that a higher aggregation level ofsearch space is constituted of a set of lower aggregation levels, forexample. Such search space structure may be called a nested structure.According to the disclosure, there is proposed designing a search spaceconsidering the nested structure. According to the disclosure, the wholesearch space may be constituted of multiple partial search spaces, andeach partial search space may be constituted of the same number ofphysical downlink control channel (PDCCH) candidates. In other words,each partial search space may be configured in the same form aspossible. The proposed structure may ensure an even performance for eachpartial search space when adjusting the number of times of blinddecoding with a scaling factor.

Further, the demodulation reference signal (DMRS) may be transmitted fordecoding the 5G download control channel. A sequence available for theDMRS should be agreed on between the base station (BS) and the UE. In apossible method, a pre-defined unique identity (ID), e.g., cell ID or UEID (e.g., radio network temporary identifier (RNTI)) may be used, or thevalue may be set for each UE via higher layer signaling (e.g., radioresource control (RRC) signaling). According to the disclosure, there isalso proposed a DMRS sequence determining method considering theinter-Tx/Rx point (TRP) index or synchronization signal block index,component carrier index, or bandwidth partial index to randomize, e.g.,(TRP) interference, beam interference, or long term evolution (LTE)co-existence interference.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, a method fortransmitting download control information in a communication systemcomprises performing mapping so that resource group units in adistributed control channel are distributed in a time and frequencyresource in a control region and transmitting the download controlinformation using the mapped resource.

According to the disclosure, there is proposed an effective interleavingmethod for distributed download control channels in a 5G communicationsystem, which may raise the diversity gain for the download controlchannel while effectively reducing the blocking probability.

According to the disclosure, the proposed structure may ensure an evenperformance for each partial search space when adjusting the number oftimes of blind decoding with a scaling factor.

According to the disclosure, the proposed method may effectivelyrandomize inter-beam interference or inter-TRP interference.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure and many of the attendant aspects thereofwill be readily obtained as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings, in which:

FIG. 1 is a view illustrating a basic structure of a time/frequencyregion in long term evolution (LTE) according to an embodiment of thedisclosure;

FIG. 2 is a view illustrating a physical downlink control channel(PDCCH) and an enhanced physical downlink control channel (EPDCCH) inLTE according to an embodiment of the disclosure;

FIG. 3 is a view illustrating a transmission resource of a downloadcontrol channel in a fifth generation (5G) communication systemaccording to an embodiment of the disclosure;

FIG. 4 is a view illustrating a download control region allocation in a5G communication system according to an embodiment of the disclosure;

FIG. 5 is a view illustrating a sync signal block structure in a 5Gcommunication system according to an embodiment of the disclosure;

FIG. 6 is a view illustrating an interleaving scheme according toembodiment 1-1 of the disclosure;

FIG. 7 is a view illustrating an interleaving scheme according toembodiment 1-2 of the disclosure;

FIG. 8 is a view illustrating an interleaving scheme according toembodiment 1-3 of the disclosure;

FIG. 9 is a view illustrating a search space of a 5G download controlchannel according to embodiment 2 of the disclosure;

FIG. 10 is a block diagram illustrating a configuration of a userequipment (UE) according to an embodiment of the disclosure; and

FIG. 11 is a block diagram illustrating a configuration of a basestation (BS) according to an embodiment of the disclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

In describing the embodiments, the description of technologies that areknown in the art and are not directly related to the disclosure isomitted. This is for further clarifying the gist of the disclosurewithout making it unclear.

For the same reasons, some elements may be exaggerated or schematicallyshown. The size of each element does not necessarily reflect the realsize of the element. The same reference numeral is used to refer to thesame element throughout the drawings.

It should be appreciated that the blocks in each flowchart andcombinations of the flowcharts may be performed by computer programinstructions. Since the computer program instructions may be equipped ina processor of a general-use computer, a special-use computer or otherprogrammable data processing devices, the instructions executed througha processor of a computer or other programmable data processing devicesgenerate means for performing the functions described in connection witha block(s) of each flowchart. Since the computer program instructionsmay be stored in a computer-available or computer-readable memory thatmay be oriented to a computer or other programmable data processingdevices to implement a function in a specified manner, the instructionsstored in the computer-available or computer-readable memory may producea product including an instruction means for performing the functionsdescribed in connection with a block(s) in each flowchart. Since thecomputer program instructions may be equipped in a computer or otherprogrammable data processing devices, instructions that generate aprocess executed by a computer as a series of operational steps areperformed over the computer or other programmable data processingdevices and operate the computer or other programmable data processingdevices may provide steps for executing the functions described inconnection with a block(s) in each flowchart.

Further, each block may represent a module, segment, or part of a codeincluding one or more executable instructions for executing a specifiedlogical function(s). Further, it should also be noted that in somereplacement execution examples, the functions mentioned in the blocksmay occur in different orders. For example, two blocks that areconsecutively shown may be performed substantially simultaneously or ina reverse order depending on corresponding functions.

As used herein, the term “unit” means a software element or a hardwareelement such as a field-programmable gate array (FPGA) or an applicationspecific integrated circuit (ASIC). A unit plays a certain role.However, the term “unit” is not limited as meaning a software orhardware element. A ‘unit’ may be configured in a storage medium thatmay be addressed or may be configured to reproduce one or moreprocessors. Accordingly, as an example, a ‘unit’ includes elements, suchas software elements, object-oriented software elements, class elements,and task elements, processes, functions, attributes, procedures,subroutines, segments of program codes, drivers, firmware, microcodes,circuits, data, databases, data architectures, tables, arrays, andvariables. A function provided in an element or a ‘unit’ may be combinedwith additional elements or may be split into sub elements or sub units.Further, an element or a ‘unit’ may be implemented to reproduce one ormore central processing units (CPUs) in a device or a securitymultimedia card.

Wireless communication systems evolve beyond voice-centered services tobroadband wireless communication systems to provide high data rate andhigh-quality packet data services, such as 3rd generation partnershipproject (3GPP) high speed packet access (HSPA), long term evolution(LTE) or evolved universal terrestrial radio access (E-UTRA)),LTE-advanced (LTE-A), LTE-pro, 3GPP2 high rate packet data (HRPD), ultramobile broadband (UMB), and institute of electrical and electronicsengineers (IEEE) 802.16e communication standards.

As a representative example of such broadband wireless communicationsystem, LTE system adopts orthogonal frequency division multiplexing(OFDM) for downlink and single carrier frequency division multipleaccess (SC-FDMA) for uplink. Uplink means a wireless link where the userequipment (UE) (or mobile station (MS) transmits data or control signalsto the base station (BS, or evolved node B (eNode B)), and downloadmeans a wireless link where the BS transmits data or control signals tothe UE. Such multiple access scheme allocates and operatestime-frequency resources carrying data or control information per usernot to overlap, i.e., to maintain orthogonality, to therebydifferentiate each user's data or control information.

Post-LTE communication systems, e.g., 5G communication systems, arerequired to freely reflect various needs of users and service providersand thus to support services that simultaneously meet variousrequirements. Services considered for 5G communication systems include,e.g., enhanced mobile broadband (eMBB), massive machine typecommunication (mMTC), and ultra reliability low latency communication(URLLC).

eMBB aims to provide a further enhanced data transmission rate ascompared with LTE, LTE-A, or LTE-pro. For example, eMBB for 5Gcommunication systems needs to provide a peak data rate of 20 Gbps ondownload and a peak data rate of 10 Gbps on uplink in terms of one basestation. 5G communication systems also need to provide an increased userperceived data rate while simultaneously providing such peak data rate.To meet such requirements, various transmit (TX)/receive (RX)techniques, as well as multiple input multiple output (MIMO), need tofurther be enhanced. While LTE currently adopts a TX bandwidth up to 20MHz in the 2 GHz band to transmit signals, the 5G communication systememploys a broader frequency bandwidth in a frequency band ranging from 3GHz to 6 GHz or more than 6 GHz to meet the data rate required for 5Gcommunication systems.

mMTC is also considered to support application services, such asinternet of things (IoT) in the 5G communication system. To efficientlyprovide IoT, mMTC is required to support massive UEs in the cell,enhance the coverage of the UE and the battery time, and reduce UEcosts. IoT terminals are attached to various sensors or devices toprovide communication functionality, and thus, it needs to support anumber of UEs in each cell (e.g., 1,000,000 UEs/km²). SincemMTC-supportive UEs, by the nature of service, are highly likely to belocated in shadow areas not covered by the cell, such as the undergroundof a building, it requires much broader coverage as compared with otherservices that the 5G communication system provides. mMTC-supportive UEs,due to the need for being low cost and difficulty in frequentlyexchanging batteries, are required to have a very long battery life,e.g., 10 years to 15 years.

URLLC is a mission-critical, cellular-based wireless communicationservice. For example, URLLC may be considered for use in remote controlfor robots or machinery, industrial automation, unmanned aerialvehicles, remote health care, or emergency alert. This requires thatURLLC provide very low-latency and very high-reliability communication.For example, URLLC-supportive services need to meet an air interfacelatency of less than 0.5 milliseconds simultaneously with a packet errorrate of 10⁻⁵ or less. Thus, for URLLC-supportive services, the 5Gcommunication system is required to provide a shorter transmit timeinterval (TTI) than those for other services while securing reliablecommunication links by allocating a broad resource in the frequencyband.

The three 5G services, i.e., eMBB, URLLC, and mMTC, may be multiplexedin one system and be transmitted. In this case, the services may adoptdifferent TX/RX schemes and TX/RX parameters to meet their differentrequirements.

The frame architecture for the LTE and LTE-A system is described belowwith reference to the drawings.

FIG. 1 is a view illustrating a basic structure of time-frequency domainwhich is radio resource domain where the data or control channel istransmitted on downlink in the LTE system according to an embodiment ofthe disclosure.

Referring to FIG. 1 , the horizontal axis refers to the time domain, andthe vertical axis refers to the frequency domain. In the time domain,the minimum transmission unit is an OFDM symbol, and Nsymb (101) OFDMsymbols come together to configure one slot 102, and two slots cometogether to configure one subframe 103. The slot is 0.5 ms long, and thesubframe is 1.0 ms long. The radio frame 104 is a time domain unitconsisting of ten subframes. In the frequency domain, the minimumtransmission unit is subcarrier, and the bandwidth of the overall systemtransmission band consists of a total of NBW (105) subcarriers. Thebasic resource unit in the time-frequency domain is resource element 106(RE), and this may be represented in OFDM symbol index and subcarrierindex. Resource block 107 (RB) or physical resource block (PRB) isdefined with Nsymb (101) continuous OFDM symbols in the time domain andNRB (108) continuous subcarriers in the frequency domain. Accordingly,one NRB 108 includes Nsymb×NRB REs (106). Generally, the minimumtransmission unit of data is RB. Generally in the LTE system, Nsymb=7,NRB=12, and, NBW and NRB are proportional to the bandwidth of systemtransmission band.

Now described is the download control information (DCI) in the LTE andLTE-A system.

In the LTE system, the scheduling information on downlink data or uplinkdata is transferred through downlink control information (DCI) from theBS to the terminal. Various formats may be defined for the DCI. Forexample, pre-defined DCI formats may be applied depending on whether thescheduling information is for uplink data or download data, whether theDCI is a compact DCI of which the size of control information is small,whether spatial multiplexing using multiple antennas applies, or whetherthe DCI is for power control. For example, DCI format 1, which is thescheduling control information about download data may be configured toinclude the following pieces of control information.

Resource allocation type 0/1 flag: notifies whether resource allocationtype is type 0 or type 1. Type 0 allocates resources in RBG (resourceblock group) units by applying bitmap scheme. In the LTE system, thebasic unit of scheduling is RB (resource block) represented in time andfrequency domain resources, and RBG consists of a plurality of RBs andbecomes the basic unit of scheduling in the type 0 scheme. Type 1 allowsfor allocation of a particular RB in the RBG.

RB assignment: notifies RB allocated for data transmission. A resourceis represented according to system bandwidth and a resource allocationscheme is determined.

Modulation and coding scheme (MCS: notifies the size of transport blockthat is data to be transmitted and modulation scheme used for datatransmission.

Hybrid automatic repeat request (HARQ) process number: notifies processnumber of HARQ.

New data indicator: notifies whether HARQ initial transmission orre-transmission.

Redundancy version: notifies redundancy version of HARQ.

Transmit power control (TPC) command for physical uplink control channel(PUCCH): notifies transmit power control command for uplink controlchannel PUCCH.

As set forth above, the DCI transmitted via the download control channelcontains the following information.

Download scheduling assignment: control information related to PDSCHresource designation, transmission format, HARQ information, or spatialmultiplexing.

Uplink scheduling grant: physical uplink shared channel (PUSCH) resourcedesignation, transmission format, HARQ information, or PUSCH powercontrol.

Power control commands for UE set: Different pieces of controlinformation typically have different DCI message sizes and these areclassified in different DCI formats. The DCI formats are brieflydescribed. The download scheduling assignment information is transmittedin DCI format 1/1A/2/1C/1D/2/2A/2B/2C, the uplink scheduling grant istransmitted in DCI format 0/4, and the power control command istransmitted in DCI format 3/3A. In general, since multiple UEs aresimultaneously scheduled for the download and uplink, multiple DCItransmissions are simultaneously carried out.

The DCI undergoes channel coding and modulation and is transmittedthrough downlink physical control channel physical downlink controlchannel (PDCCH) or enhanced PDCCH (EPDCCH).

The cyclic redundancy check (CRC) is added to the DCI message payload,and the CRC is scrambled with the radio network temporary identifier(RNTI) that is the identity of the UE. Different RNTIs are used for thepurposes of the DCI message, e.g., UE-specific data transmission, powercontrol command, or random access response. The RNTI is not explicitlytransmitted, but the RNTI is included in the CRC calculation process andtransmitted. Upon receiving the DCI message transmitted on the PDCCH,the UE identifies the CRC using the allocated RNTI, and when the CRC isidentified to be correct, the UE may be aware that the message has beentransmitted thereto.

The download control channels for the LTE and LTE-A system are describedbelow in detail with reference to the drawings.

FIG. 2 is a view illustrating download physical channels, a PDCCH 201and an enhanced PDCCH (EPDCCH) 202 where the LTE DCI is transmittedaccording to an embodiment of the disclosure.

Referring to FIG. 2 , the PDCCH 201 is time-multiplexed with the PDSCH203, which is a data transmission channel, and is transmitted over theoverall system bandwidth. The region for the PDCCH 201 is representedwith the number of OFDM symbols, and this is indicated to the UE via thecontrol format indicator (CFI) that is transmitted via the physicalcontrol format indicator channel (PCFICH). The PDCCH 201 may beallocated to the OFDM symbols which are positioned in the head of thesubframe, allowing the UE to decode the download scheduling allocationas quick as possible. This provides the advantage of being able toreduce the decoding latency for download shared channel (DL-SCH), i.e.,the overall download transmission latency. Since one PDCCH carries oneDCI message, and multiple UEs may simultaneously be scheduled for thedownload and uplink, multiple PDCCHs are simultaneously transmitted ineach cell.

As a reference signal for decoding the PDCCH 201, the cell-specificreference signal (CRS) 204 is used. The CRS 204 is transmitted in eachsubframe over the entire band, and the scrambling and resource mappingare varied depending on the cell identity (ID). Since the CRS 204 is areference signal commonly used for all the UEs, UE-specific beamformingcannot be used. Accordingly, the multi-antenna TX scheme for LTE PDCCHis limited to open-loop TX diversity. The number of CRS ports isimplicitly known to the UE from the decoding of the physical broadcastchannel (PBCH).

The resource allocation of the PDCCH 201 is based on the control-channelelement (CCE), and one CCE is constituted of nine REGs, i.e., a total of36 REs. The number of CCEs necessary for a particular PDCCH 201 may be1, 2, 4, or 8, and this differs depending on the channel coding rate ofthe DCI message payload. As such, different numbers of CCEs are used toimplement the link adaptation of the PDCCH 201.

The UE needs to detect a signal while it is unaware of the informationabout the PDCCH 201. LTE defines the search space that denotes a set ofCCEs for blind decoding. The search space consists of a plurality ofsets in the aggregation level (AL) of each CCE, and this is notexplicitly signaled but is implicitly defined via the function andsubframe number by the identity of the UE. In each subframe, the UEdecodes the PDCCH 201 for all possible resource candidates that may becreated from the CCEs in the set search space and processes theinformation declared by the CRC check to be valid for the UE.

The search space is divided into a UE-specific search space and a commonsearch space. A predetermined group of UEs or all the UEs mayinvestigate the common search space of the PDCCH 201 to receivecell-common control information, e.g., paging message, or dynamicscheduling for system information. For example, scheduling allocationinformation about DL-SCH for transmitting system information block(SIB)-1 containing, e.g., cell service provider information may bereceived by investigating the common search space of the PDCCH 201.

Referring to FIG. 2 , the EPDCCH 202 is frequency-multiplexed with thePDSCH 203 and is transmitted. The BS may properly allocate the resourcesof the EPDCCH 202 and the PDSCH 203 via scheduling, thus able toeffectively support coexistence with data transmission for existing LTEUEs. However, since the EPDCCH 202 is allocated and transmitted in oneoverall subframe on the time axis, there may be a loss in terms oftransmission latency time. Multiple EPDCCHs 202 constitute one EPDCCH(202) set, and the EPDCCH (202) set is allocated per PRB pair. Thelocation information about the EPDCCH set is set UE-specifically, andthis is signaled via radio resource control (RRC). Up to two EPDCCHssets may be set for each UE, and one EPDCCH set may simultaneously bemultiplexed and set for different UEs.

The resource allocation of the EPDCCH 202 is performed based on theenhanced CCE (ECCE), and one ECCE may be constituted of four or eightenhanced REGs (EREGs), and the number of EREGs per ECCE may be varieddepending on the CP length and subframe configuration information. OneEREG consists of nine REs, and thus, there may be 16 EREGs per PRB pair.EPDCCH transmissions are divided into localized/distributedtransmissions depending on the EREG RE mapping scheme. The ECCEaggregation level may be 1, 2, 4, 8, 16, or 32, and this is determinedby the CP length, subframe configuration, EPDCCH format, or transmissionscheme.

The EPDCCH 202 only supports the UE-specific search space. Accordingly,the UE, which desires to receive the system message, needs toinvestigate the common search space on the existing PDCCH 201.

Unlike the PDCCH 201, the EPDCCH 202 adopts the demodulation referencesignal (DMRS) 205 as a reference signal for decoding. Thus, theprecoding of the EPDCCH 202 may be set by the base station, andUE-specific beamforming may be used. The UEs may decode the EPDCCH 202via the DMRS 205 even though they are unaware what precoding has beenused. The EPDCCH 202 adopts the same pattern as the DMRS of the PDSCH203. However, unlike the PDSCH 203, the DMRS 205 of the EPDCCH 202 isable to support transmission using up to four antenna ports. The DMRS205 is transmitted only in the PRB where the EPDCCH is transmitted.

The port configuration information about the DMRS 205 is varieddepending on the transmission scheme of the EPDCCH 202. In the case oflocalized transmission, the antenna port corresponding to the ECCE towhich the EPDCCH 202 is mapped is selected based on the UE ID. Wheredifferent UEs share the same ECCE, i.e., when multi-user MIMOtransmission is used, the DMRS antenna port may be allocated to each UE.Alternatively, the DMRS 205 may be shared and transmitted in which caseit may be differentiated by the DMRS (205) scrambling set by higherlayer signaling. In the case of distributed transmission, two DMRS (205)antenna ports are supported, and a precoder cycling type of diversityscheme is supported. The DMRS 205 may be shared for all the REstransmitted in one PRB pair.

Now described in greater detail is the search space for transmittingdownload control channels in LTE and LTE-A.

In LTE, the overall PDCCH region is constituted of a CCE set in thelogical region, and there is a search space constituted of a set ofCCEs. The search space is divided into the common search space and theUE-specific search space, and the search space for LTE PDCCH may bedefined as follows.

Refer to Table 1 below in connection with this.

TABLE 1 The set of PDCCH candidates to monitor are defined in terms ofsearch spaces, where a search space S_(k) ^((L)) at aggregation level L∈ {1,2,4,8} is defined by a set of PDCCH candidates. For each servingcell on which PDCCH is monitored, the CCEs corresponding to PDCCHcandidate m of the search space S_(k) ^((L)) are given by L {(Y_(k) +m′) mod └N_(CCE,k) / L┘}+ i where Y_(k) is defined below, i = 0,...,L−1. For the common search space m′ = m . For the PDCCH UE specific searchspace, for the serving cell on which PDCCH is monitored, if themonitoring UE is configured with carrier indicator field then m′ = m +M^((L)) · n_(CI) where n_(CI) is the carrier indicator field value, elseif the monitoring UE is not configured with carrier indicator field thenm′ = m , where m = 0,...,M^((L)) −1 . M^((L)) is the number of PDCCHcandidates to monitor in the given search space. Note that the carrierindicator field value is the same as ServCellIndex. For the commonsearch spaces, Y_(k) is set to 0 for the two aggregation levels L = 4and L = 8 . For the UE-specific search space S_(k) ^((L)) at aggregationlevel L , the variable Y_(k) is defined by Y_(k) =(A·Y_(k−1))mod D whereY⁻¹ = n_(RNTI) ≠ 0 , A = 39827 , D = 65537 and k = └n_(s)/2┘ , n_(s) isthe slot number within a radio frame. The RNTI value used for n_(RNTI)is defined in subclause 7.1 in downlink and subclause 8 in uplink.

According to the definition of the search space for the PDCCH describedabove, the UE-specific search space is not explicitly signaled but isimplicitly defined via the subframe number and function by the identityof the UE. In other words, the UE-specific search space may be varieddepending on the subframe number, meaning that it may be varieddepending on times. This addresses the problem that a particular UEamong UEs cannot use the search space due to the other UEs (this issueis defined as ‘blocking’.) Where a certain UE cannot be scheduled in asubframe because all the CCEs that it investigates are already in use byother UEs scheduled in the same subframe, such issue may not occur inthe next subframe because the search space is varied over time. Forexample, although the UE-specific search spaces of UE #1 and UE #2partially overlap each other in a particular subframe, the overlap maybe predicted to differ in the next subframe because the UE-specificsearch space is varied per subframe.

According to the definition of the search space for the PDCCH describedabove, the common search space is defined as a set of CCEs previouslyagreed on because a predetermined group or UEs or all the UEs need toreceive the PDCCH. In other words, the common search space does not varydepending on, e.g., the identity of the UE or subframe number. Althoughthe common search space exists for transmission of various systemmessages, it may also be used to transmit the control information forindividual UEs. Thus, the common search space may be used to address theUE's failure to be scheduled due to insufficient available resources inthe UE-specific search space.

The search space is a set of candidate control channels constituted ofCCEs that the UE needs to attempt to decode on the aggregation level,and since there are several aggregation levels to bundle up one, two,four, or eight CCEs, the UE has a plurality of search spaces. The numberof PDCCH candidates that the UE needs to monitor in the search spacedefined as per the aggregation level in the LTE PDCCH may be defined asshown in Table 2 below.

TABLE 2 Search space S_(k) ^((L)) Number of Aggregation Size PDCCH Typelevel L [in CCEs] candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 162 Common 4 16 4 8 16 2

Referring to Table 2, the UE-specific search space supports aggregationlevel {1, 2, 4, 8}, where it has {6, 6, 2, 2} PDCCH candidates,respectively. The common-specific search space supports aggregationlevel {4, 8}, where it has {4, 2}PDCCH candidates, respectively. Thecommon search space only supports {4, 8} aggregation levels for makingbetter the coverage property because the system message is generallyrequired to reach the cell border.

The DCI transmitted in the common search space is defined only forparticular DCI formats, e.g., 0/1A/3/3A/1C, which are ones for the powercontrol purpose for the UE group or system message. In the common searchspace, the DCI formats having spatial multiplexing are not supported.The download DCI format that should be decoded in the UE-specific searchspace is varied depending on the transmission mode set for the UE. Sincethe transmission mode is set via RRC signaling, the exact subframenumber as to whether the setting is effective for the UE is notdesignated. Accordingly, the UE may be operated not to losecommunication by always performing decoding on DCI format 1A regardlessof the transmission mode.

The download control channels in the 5G communication system aredescribed below in detail with reference to FIGS. 3, 4, and 5 .

FIG. 3 is a view illustrating an example of a basic unit of time andfrequency resource constituting a download control channel available in5G according to an embodiment of the disclosure.

Referring to FIG. 3 , the basic unit (i.e., the resource element group(REG) of the time and frequency resource constituting the controlchannel includes one OFDM symbol 301 along the time axis and 12subcarriers 302 along the frequency axis—i.e., one RB. By assuming oneOFDM symbol 301 as the basic unit on the time axis in constituting thebasic unit of the control channel, the data channel and the controlchannel may be time-multiplexed in one subframe. By leaving the controlchannel ahead of the data channel, the user's processing time may bereduced, making it easier to meet the latency time requirements. Bysetting the basic unit on the frequency axis for the control channel toone RB, frequency multiplexing between the control channel and the datachannel may be carried out more efficiently.

Various sizes of control channel regions may be configured by joiningREGs 303 as shown in FIG. 3 . As an example, where the basic unit inwhich the download control channel is allocated in 5G is the CCE 304,one CCE 304 may consist of multiple REGs 303. For example, when the REG303 of FIG. 3 may consist of 12 REs, and one CCE 304 consists of sixREGs 303, the CCE 304 may consist of 72 REs. When the download controlregion is set, the region may be constituted of multiple CCEs 304, and aparticular download control channel may be mapped to one or more CCEs304 according to the aggregation level (AL) in the control region and betransmitted. The CCEs 304 in the control region may be distinguishedwith numbers in which case the numbers may be assigned according to alogical mapping scheme.

The basic unit, i.e., the REG 303, of the download control channel shownin FIG. 3 may contain REs to which the DCI is mapped and the region towhich the DMRS 305, a reference signal for decoding the REs, is mapped.The DMRS 305 may be mapped and transmitted considering the number ofantenna ports used to transmit the download control channel. Meanwhile,where two antenna ports (e.g., antenna port #0 and antenna port #1) areused as an example, the DMRS transmitted for antenna port #0 and theDMRS transmitted for antenna port #1 may exist. The DMRSs for thedifferent antenna ports may be multiplexed in various manners. Further,the DMRSs corresponding to different antenna ports may be transmittedorthogonal to each other in different REs. As such, the DMRSs may befrequency division multiplexed (FDMed) and transmitted or may be codedivision multiplexed (CDMed) and transmitted. Other various types ofDMRS patterns may exist, which may be associated with the number ofantenna ports.

FIG. 4 is a view illustrating an example of a control region (controlresource set (CORESET)) where the download control channel istransmitted in the 5G wireless communication system of the disclosure.

Referring to FIG. 4 , an example in which two control regions (controlresource set #1 401 and control resource set #2 402) are set in one slot420 on the time axis while the system bandwidth 410 is set on thefrequency axis. Although in the example illustrated in FIG. 4 one slotconsists of seven OFDM symbols, this is merely an example for ease ofdescription, and embodiments of the disclosure are not limited thereto.The control resource sets numbers 401 and 402 may be set to a particularsubband 403 in the overall system bandwidth 410 on the frequency axis.One or more OFDM symbols may be set on the time axis, which may bedefined as control resource set duration 404. FIG. 4 illustrates anexample in which control resource set #1 401 is set to two-symbolcontrol resource set duration, and control resource set #2 402 is set toone-symbol control resource set duration.

The above-described 5G control region may be set via higher layersignaling (e.g., system information or RRC signaling) from the BS to theUE. Setting a control region for a UE may mean that providing the UEwith information such as the location of the control region, subband,resource allocation of the control region, and control resource setduration. For example, the information provided may contain at least oneor more of pieces of information shown in Table 3 below.

TABLE 3 - configuration information 1. frequency-axis RB allocationinformation - configuration information 2. control region start symbol -configuration information 3. control resource set duration -configuration information 4. REG bundling size - configurationinformation 5. transmission mode (interleaved transmission scheme ornon-interleaved transmission scheme) - configuration information 6.search space type (common search space, group- common search space,UE-specific search space) - configuration information 7. monitoringperiod - others

Besides the above-described configuration information, various pieces ofinformation necessary to transmit the download control channel may beset for the UE.

A structure in which the sync signal and the PBCH are transmitted in the5G communication system is described below.

FIG. 5 is a view illustrating a synchronization signal (SS) block 500considered for 5G communication systems according to an embodiment ofthe disclosure.

Referring to FIG. 5 , the synchronization signal block 500 includes aprimary synchronization signal (PSS) 501, a secondary synchronizationsignal (SSS) 503, and a physical broadcast channel (PBCH) 502.

The PSS 501 and the SSS 503 may be transmitted in 12 RBs 505 on thefrequency axis and in one OFDM symbol 504 on the time axis. In 5G, atotal of 1,008 different cell IDs may be defined, the PSS 501 may havethree different values depending on the physical layer ID of the cell,and the SSS 503 may have 336 different values. The UE may be aware ofone of the 1,008 cell IDs in combination via detection of the PSS 501and SSS 503. The cell ID may be represented in Equation 1 below.N _(ID) ^(cell)=3N _(ID) ⁽¹⁾ +N _(ID) ⁽²⁾  Equation 1

N⁽¹⁾ _(ID) may be estimated from the SSS 503, which has a value rangingfrom 0 to 335. N⁽²⁾ _(ID) may be estimated from the PSS 501, which has avalue ranging from 0 to 2. N⁽¹⁾ _(ID) By combining with N⁽²⁾ _(ID), thecell ID, N^(cell) _(ID), may be estimated. However, Equation 1 describedabove is merely an example method for estimating the cell ID, and thecell ID may also be estimated by other equations.

The PBCH 502 may be transmitted in 24 RBs 506 on the frequency axis andin two OFDM symbols 504 on the time axis. In the PBCH 502, variouspieces of system information called MIB may be transmitted, and at leastany one of the contents shown in Table 4 below may be transmitted.

TABLE 4 - (part of) SFN: [7-10] bits * at least 80ms granularity -[H-SFN: 10 bits] - timing information in radio frame: [0-7] bits * e.g.,SS block time index: [0-6] bits * e.g., half radio frame timing: [0-1]bits - remaining minimum system information (RMSI) schedulinginformation: [x] bits * control resource set(s) (CORESET(s))information: [x] bits - simplified information of CORESET(s)configuration - [RMSI numerology: [0-2] bits] * frequencyresource-related information for physical download shared channel(PDSCH) scheduling: [x] bits - bandwidth part-related information: [x]bits - information for quick identification that there is nocorresponding RMSI to the PBCH: [0-1] bits - [SS burst set periodicity:[0-3] bits] - [area ID: x bits] - [value tag: x bits] - [information ontracking RS: x bits] - reserved bits: [x>0] bits

As set forth above, the synchronization signal block 500 consists of thePSS 501, the SSS 503, and the PBCH 502 and may be mapped with a total offour OFDM symbols on the time axis. Since the transmission bandwidth (12RBs 505) for the PSS 501 and the SSS 503 differs from the transmissionbandwidth (24 RBs 506) for the PBCH 502, the OFDM symbols where the PSS501 and the SSS 503 are transmitted in the PBCH (502) transmitted band(24 RBs 506) may have 6 RBs (e.g., 507 and 508 of FIG. 5 ) on both sidesexcept for the 12 RBs in the middle where the PSS 501 and the SSS 503are transmitted, and the resource blocks 507 and 508 in FIG. 5 may beused for transmitting other signals or may be empty. Reference number510 represents an example of an OFDM symbol that can be associated withthe 6 RBs 507.

According to the disclosure, there is proposed a method for transmittinga distributed or interleaved download control channel, i.e., PDCCH, inthe 5G wireless communication system.

According to the disclosure, 5G wireless communication systems supportmethods for transmitting download control channels, particularlydistributed or interleaving transmission methods and localized ornon-interleaving transmission methods. Distributed transmission methodsmay adopt interleaver or distributed mapping to maximize frequency-axisdiversity. The resource distribution for a particular download controlchannel may be carried out in REG bundle size. At this time, one or morecontrol resource sets (CORESETs) may be set in the system bandwidth, andcontrol regions set with different system parameters may be configuredto overlap on the same time/frequency resource. In this case, thecontrol channel distribution method of one control region in theoverlapping region may influence the transmission of the downloadcontrol channel in another control region. For example, where twodifferent control regions with different REG bundle sizes wholly orpartially overlap each other in the time/frequency resource, theblocking probability between the two control regions may increasedepending on the interleaving or resource distribution scheme. Theblocking probability may mean the probability of failing to transmit aPDCCH candidate as another PDCCH candidate is transmitted. Thus, a needexists for designing an interleaver capable of effectively obtainingdiversity while reducing the blocking probability. According to thedisclosure, there are proposed, as methods for transmitting adistributed download control channel, a method for performinginterleaving in some RB sets constituting the control region, a methodfor performing interleaving at particular RB intervals, and a method forperforming interleaving with an offset set to each control region. Alsoproposed are interleaving parameters capable of randomizing varioustypes of interference.

Minimizing power consumption due to the UE's blind decoding is verycritical in designing the search space of the 5G download controlchannel. To that end, upon blind decoding each control channelcandidate, it may be considered to reuse the channel estimation valueused for prior decoding. For that purpose, the search space may bedesigned so that a higher aggregation level of search space isconstituted of a set of lower aggregation levels, for example. Suchsearch space structure may be called a nested structure. According tothe disclosure, there is proposed designing a search space consideringthe nested structure. According to the disclosure, the whole searchspace may be constituted of multiple partial search spaces, and eachpartial search space may be constituted of the same number of PDCCHcandidates. In other words, each partial search space may be configuredin the same form as possible. According to the disclosure, the proposedstructure may ensure an even performance for each partial search spacewhen adjusting the number of times of blind decoding with a scalingfactor.

The DMRS may be transmitted for decoding the 5G download controlchannel. A sequence available for the DMRS should be agreed on betweenthe BS and the UE. In an example method therefor, a pre-defined uniqueidentity (ID), e.g., cell ID or UE ID (e.g., RNTI) may be used, or thevalue may be set for each UE via higher layer signaling (e.g., RRCsignaling). According to the disclosure, there is provided a method fordetermining the DMRS sequence of the download control channel given thebeam operation considered in the 5G communication system. According tothe disclosure, the proposed method may effectively randomize inter-beaminterference or inter-TRP interference.

Hereinafter, embodiments of the disclosure are described in detail withreference to the accompanying drawings. Further, although LTE or LTE-Asystem is described in connection with embodiments of the disclosure, asan example, embodiments of the disclosure may also apply to othercommunication systems with similar technical background or channel form.For example, embodiments of the disclosure may also be applicable topost-LTE-A, 5G mobile communication technology (e.g., new radio (NR)).Further, embodiments of the disclosure may be modified in such a rangeas not to significantly depart from the scope of the disclosure underthe determination by one of ordinary skill in the art and suchmodifications may be applicable to other communication systems.

First Embodiment

According to a first embodiment of the disclosure, there is proposed aninterleaving method (or a method for evenly distributing resources) forthe distributed PDCCH.

As set forth above, the minimum transmission unit for the PDCCH in 5G isthe control channel element (CCE), and one CCE may consist of a total ofsix REGs. To raise channel estimation capability, multiple REGs mayconstitute one REG bundle, and resources may be allocated so that theREGs constituting one REG bundle are positioned adjacent each other inthe time and frequency resources. That is, the REG bundle may belocalized. In the distributed PDCCH, one CCE may be mapped to bedistributed in REG bundle units in the time and frequency resources inthe control region, which may be carried out by a particular interleaverfunction (or distribution mapping method). At this time, the minimumunit of the interleaving may be the REG bundle. For example, theresources of the overall control region may be indexed in REG bundleunits and may be entered as inputs to the interleaver function, and theoutputs of the interleaver function may be interleaved REG bundleindexes. This may be summarized and represented as shown in Table 5below.

TABLE 5 The CCE-to-REG mapping for a control-resource set can beinterleaved or non- interleaved, configured by the higher-layerparameter CORESET_Trans_type, and is described by REG bundles, - REGbundle i is defined as REGs {i,iL+1,...,iL+L−1}where L∈{2,6} is the REGbundle size configured by the higher-layer parameterCORESET_REG_bundle_size and i=0,1,...,N_(REG) ^(CORESET)/L−1 is thenumber of REGs in the CORESET - CCE j consists of REG bundles{f(6j/L),f(6j/L+1),...,f(6j/L+6/L−1)} where f(x)is an interleaver Forinterleaved CCE-to-REG mapping, L∈{2,6} for N_(symb) ^(CORESET)=1 andL∈{N_(symb) ^(CORSET),6} for N_(symb) ^(CORESET)∈{2,3}

For example, the interleaver function may follow the methods below(e.g., interleaving method 1 and interleaving method 2).

[Interleaving Method 1]

The input to the block interleaver may be the REG bundle. Aninterleaving matrix may be generated, and the indexes may be selectedand output in the order of the rows in the interleaving matrix.

Meanwhile, interleaving method 1 may be expressed in Tables 6 and 7below.

TABLE 6  The input to the block interleaver are REG bundle indicesdenoted by d₁, d₂, . . . , d_(D), where D is the number of REG bundleindices. The output index sequence from the block interleaver is derivedas follows,  (1) Assign C_(subblock) ^(CC) = 32 to be the number ofcolumns of the matrix. The columns of the matrix are numbered 0, 1, 2, .. . , C_(subblock) ^(CC) − 1 from left to right.  (2) Determine thenumber of rows of the matrix R_(subblock) ^(CC), by finding minimuminteger R_(subblock) ^(CC) such that,  D ≤ (R_(subblock) ^(CC) ×C_(subblock) ^(CC))  The rows of rectangular matrix are numbered 0, 1,2, . . . , R_(subblock) ^(CC) − 1 from top to bottom.  (3) If(R_(subblock) ^(CC) × C_(subblock) ^(CC)) > D, then N_(D) =(R_(subblock) ^(CC) × C_(subblock) ^(CC) − D) dummy indices are paddedsuch that y_(k) = <NULL> for k = 0, 1, . . . , N_(D) − 1. Then, y_(N)_(D) _(+k) = d_(k) ^((i)), k = 0, 1, . . . , D-1, and the index sequencey_(k) is written into the (R_(subblock) ^(CC) × C_(subblock) ^(CC))matrix row by row starting with bit y₀ in column 0 of row 0,$\begin{bmatrix}y_{0} & y_{1} & y_{2} & \ldots & y_{C_{subblock}^{CC} - 1} \\y_{C_{subblock}^{CC}} & y_{C_{subblock}^{CC} + 1} & y_{C_{subblock}^{CC} + 2} & \ldots & y_{{2C_{subblock}^{CC}} - 1} \\\vdots & \vdots & \vdots & \ddots & \vdots \\y_{{({R_{subblock}^{CC} - 1})} \times C_{subblock}^{CC}} & y_{{{({R_{subblock}^{CC} - 1})} \times C_{subblock}^{CC}} + 1} & y_{{{({R_{subblock}^{CC} - 1})} \times C_{subblock}^{CC}} + 2} & \ldots & y_{({{R_{subblock}^{CC} \times C_{subblock}^{CC}} - 1})}\end{bmatrix}\quad$  (4) Perform the inter-column permutation for thematrix based on the pattern 

P(j) 

_(j∈{0,1,...,C) _(subblock) _(CC) _(−1}) that is shown in table below,where P(j) is the original column position of the j-th permuted column.After permutation of the columns, the inter-column permuted(R_(subblock) ^(CC) × C_(subblock) ^(CC)) matrix is equal to$\begin{bmatrix}y_{P{(0)}} & y_{P{(1)}} & y_{P{(2)}} & \ldots & y_{P{({C_{subblock}^{CC} - 1})}} \\y_{{P{(0)}} + C_{subblock}^{CC}} & y_{{P{(1)}} + C_{subblock}^{CC}} & y_{{P{(2)}} + C_{subblock}^{CC}} & \ldots & y_{{P{({C_{subblock}^{CC} - 1})}} + C_{subblock}^{CC}} \\\vdots & \vdots & \vdots & \ddots & \vdots \\y_{{P{(0)}} + {{({R_{subblock}^{CC} - 1})} \times C_{subblock}^{CC}}} & y_{{P{(1)}} + {{({R_{subblock}^{CC} - 1})} \times C_{subblock}^{CC}}} & y_{{P{(2)}} + {{({R_{subblock}^{CC} - 1})} \times C_{subblock}^{CC}}} & \ldots & y_{{P{({C_{subblock}^{CC} - 1})}} + {{({R_{subblock}^{CC} - 1})} \times C_{subblock}^{CC}}}\end{bmatrix}\quad$  (5) The output of the block interleaver is theindex sequence read out column by column from the inter-column permuted(R_(subblock) ^(CC) × C_(subblock) ^(CC)) matrix. The indices aftersub-block interleaving are denoted by v₀ ^((i)), v₁ ^((i)), v₂ ^((i)), .. . , v_(K) _(Π) ⁻¹ ^((i)), where v₀ ^((i)) corresponds to y_(P(0)), v₁^((i)) to y_(P(0)+C) _(subblock) _(CC) . . . and K_(Π) = (R_(subblock)^(CC) × C_(subblock) ^(CC))

TABLE 7 Inter-column permutation pattern for sub-block interleaver.Number of columns Inter-column permutation pattern C_(subblock) ^(CC)<P(0), P(1), . . . , P(C_(subblock) ^(CC) − 1)> 32 <1, 17, 9, 25, 5, 21,13, 29, 3, 19, 11, 27, 7, 23, 15, 31, 0, 16, 8, 24, 4, 20, 12, 28, 2,18, 10, 26, 6, 22, 14, 30>

[Interleaving Method 2]

Input value: REG bundle index sequence={d(n), n=0, 1, 2, . . . ,N_(REGb)−1}.

In the foregoing, N_(REGb) may correspond to the total number of REGbundles in the control region, and d(n) may correspond to the nth REGbundle index.

Interleaving matrix generation: generates a matrix of C×C′ size asfollows.

$\begin{bmatrix}{d(0)} & {d(1)} & {d(2)} & \cdots & {d\left( {C - 1} \right)} \\{d(C)} & {d\left( {C + 1} \right)} & {d\left( {C + 2} \right)} & \cdots & {d\left( {{2C} - 1} \right)} \\ \vdots & \vdots & \vdots & \ddots & \vdots \\{d\left( {C \times \left( {C^{\prime} - 1} \right)} \right)} & {d\left( {C \times \left( {C^{\prime} - 1} \right)} \right)} & {d\left( {{C \times \left( {C^{\prime} - 1} \right)} + 1} \right)} & \cdots & {d\left( {N_{REGb} - 1} \right)}\end{bmatrix}$

Output value: the indexes may be selected and output in the order of therows in the interleaving matrix.

Meanwhile, in the foregoing, C=N_(CCE_REGb), i.e., the number of REBbundles per CCE, and C′=N_(CCE), the total number of CCEs in the controlregion.

The interleaving scheme may be designed given the circumstance wheredifferent control regions overlap. For example, the BS may be configuredso that control region #1 and control region #2 overlap in a particulartime and frequency resource. In this case, PDCCH candidate #1 which maybe transmitted in control region #1 may overlap PDCCH candidate #2 whichmay be transmitted in control region #2. Thus, upon transmitting PDCCHcandidate #1, PDCCH candidate #2 may not be transmitted (this may becalled ‘blocking’). The blocking probability may increase as controlregions with different pieces of configuration information overlap. Forexample, in the following cases, the blocking probability may furtherincrease. In other words, where control regions with different symbollengths overlap each other, where control regions configured withdifferent REG bundle sizes overlap each other, or where control regionsconfigured with different transmission methods (e.g., distributed orlocalized) overlap each other, the blocking probability may furtherincrease.

Accordingly, interleaving needs to be designed to minimize the blockingprobability given the above cases. Described below are interleavingmethods according to embodiments of the disclosure.

Embodiment 1-1

According to embodiment 1-1 of the disclosure, there is provided amethod for performing interleaving on the distributed PDCCH, in whichall the REG bundles may be divided in particular groups, andinterleaving on the REG bundles may be performed in each REG bundlegroup.

FIG. 6 is a view illustrating an interleaving scheme according toembodiment 1-1 of the disclosure.

Referring to FIG. 6 , one control region 600 (e.g., a CORESET) as anexample, in which the control region 600 may include a total of eightCCEs 601. One CCE 601 may consist of one or more REG bundles 602. FIG. 6illustrates an example in which the CCE 601 consists of two REG bundles602. Alternatively, the CCE 601 may include three or more REG bundles602. Meanwhile, FIG. 6 illustrates a scenario case where the overallcontrol region 600 consists of a total of 16 REG bundles 602.

The M REG bundles 602 in the control region 600 may be divided into N(≥1) groups, and each group may consist of M/N REG bundles 602. FIG. 6illustrates an example in which all the REG bundles 602 are divided intotwo groups, e.g., group #1 608 and group #2 609. Each REG bundle groupmay include a total of eight REG group bundles 602. Reference number 605represents an example of X PRBs that can be associated with the group #1608.

The BS may set the size or number of REG bundle groups for the UE. TheBS may also set the number of RBs to perform grouping for the UE. Forexample, the BS may set X RBs, which are resources in the frequencyregion to perform grouping as shown in FIG. 6 .

The BS may notify the UE of the settings related to the REG bundle groupvia higher layer signaling (e.g., RRC signaling). Or, the number of REGbundle groups may be implicitly determined with different systemparameters. For example, it may be determined by a function for thetotal number of REG bundles in the control region.

Or, the number of REG bundle groups may be fixed with the systemparameter.

In the method for determining the REG bundle group, the REGsconstituting one REG bundle group may be a set of the REGs present inthe X RBs in the control region. At this time, X may be an integermultiple of 6 RBs. Where X is an integer multiple of 6, if the controlregion with a REG bundle size of 6 REGs or the control region set in thelocalized transmission scheme overlaps the control region with adifferent setting, it may assist in minimizing the blocking probability.

Interleaving may be performed in the REG bundle group. For example,referring to FIG. 6 , interleaving 606 may be performed on REG bundlegroup #1 608, and interleaving 607 may be performed on REG bundle group#2 609. As the interleaving scheme, the above-described interleavingmethod 1 and interleaving method 2 may be used. In this case, the inputvalue for the interleaving may, rather than the set of all the REGindexes in the overall control region, be a set of the REG bundleindexes present in a particular REG bundle group in the control region.A specific example of embodiment 1-1 of the disclosure is described indetail with reference to interleaving method 2.

[Interleaving Method 3]

Input value: REG bundle index sequence={d(n), n=0, 1, 2, . . . ,N_(REGb)/N−1}.

In the foregoing, N_(REGb) may correspond to the total number of REGbundles in the control region, N may correspond to the number of REGbundle groups, and d(n) may correspond to the nth REG bundle index inthe REG bundle group.

Interleaving matrix generation: generates a matrix of C×C′ size asfollows.

$\begin{bmatrix}{d(0)} & {d(1)} & {d(2)} & \cdots & {d\left( {C - 1} \right)} \\{d(C)} & {d\left( {C + 1} \right)} & {d\left( {C + 2} \right)} & \cdots & {d\left( {{2C} - 1} \right)} \\ \vdots & \vdots & \vdots & \ddots & \vdots \\{d\left( {C \times \left( {C^{\prime} - 1} \right)} \right)} & {d\left( {C \times \left( {C^{\prime} - 1} \right)} \right)} & {d\left( {{C \times \left( {C^{\prime} - 1} \right)} + 1} \right)} & \cdots & {d\left( N_{REGb} \right)}\end{bmatrix}$

In the above example, C=N_(CCE_REGb), i.e., the number of REG bundlesper CCE. In the above example, =N_(CCE), may correspond to the totalnumber of the CCEs in the REG bundle group.

Output value: the indexes may be selected and output in the order of therows in the interleaving matrix.

As described above, one CCE may be constituted of the REG bundle indexset after interleaving. That is, CCE j may be constituted of the REGbundle (f(6j/L), f(6j/L+1), . . . , f(6j/L+6/L−1)), and f(⋅) maycorrespond to the interleaver function.

Meanwhile, the BS may provide the UE with the configuration information(e.g., X or the number of REG bundle groups) related to theabove-described interleaving via higher layer signaling, e.g., RRCsignaling. After receiving the REG bundle group-related configurationinformation from the base station, the UE may appreciate theinterleaving scheme of the control region according to the setting andmay blind-decode the download control region in the control region afterassuming the interleaving scheme.

Embodiment 1-2

According to embodiment 1-2 of the disclosure, there is provided amethod for performing interleaving on the distributed PDCCH, in whichthe REG bundles constituting one CCE may be interleaved at as constantintervals as possible, e.g., at intervals of Y. Here, Y may be set forthe UE by the BS or may be defined as a value fixed in the systemparameter. Where Y is set, the Y value may be provided from the BS tothe UE via higher layer signaling, e.g., RRC signaling.

FIG. 7 is a view illustrating an interleaving scheme according toembodiment 1-2 of the disclosure.

Referring to FIG. 7 , the control region 700 (e.g., a CORESET) includesa total of 18 REG bundles 701, and one CCE 702 consists of three REGbundles 701, for example. In this case, interleaving may be performed sothat the three REG bundles 701 constituting the CCE 702 are distributedat constant intervals (e.g., intervals of Y 703) on the frequency axis.For example, in the example of FIG. 7 , Y=6, and thus, REG bundles {0,6, 12} (701) may constitute one CCE 702. Where Y=4, REG bundles {0, 4,8} may constitute one CCE.

In determining Y, Y may be an integer multiple of 6. Where Y is aninteger multiple of 6, if the control region with a REG bundle size of 6REGs or the control region set in the localized transmission schemeoverlaps the control region with a different setting, it may assist inminimizing the blocking probability. A specific example of embodiment1-2 of the disclosure is described in detail with reference tointerleaving method 2.

[Interleaving Method 4]

Input value: REG bundle index sequence={d(n), n=0, 1, 2, . . . ,N_(REGb)−1}.

N_(REG)b may correspond to the total number of the REG bundles in thecontrol region. d(n) may correspond to the nth REG bundle index.

Interleaving matrix generation: generates a matrix of C×C′ size asfollows.

$\begin{bmatrix}{d(0)} & {d(1)} & {d(2)} & \cdots & {d\left( {C - 1} \right)} \\{d(C)} & {d\left( {C + 1} \right)} & {d\left( {C + 2} \right)} & \cdots & {d\left( {{2C} - 1} \right)} \\ \vdots & \vdots & \vdots & \ddots & \vdots \\{d\left( {C \times \left( {C^{\prime} - 1} \right)} \right)} & {d\left( {C \times \left( {C^{\prime} - 1} \right)} \right)} & {d\left( {{C \times \left( {C^{\prime} - 1} \right)} + 1} \right)} & \cdots & {d\left( {{C \times C^{\prime}} - 1} \right)}\end{bmatrix}$

C′ may be a value settable by the BS or may correspond to a value fixedin the system parameter. In the above example, it may be a valuecorresponding to C=ceil(N_(REGb)/C′). ceil(x) is the function to outputthe smallest integer among x or larger numbers. Where C×C>N_(REGb),d(N_(REGb)), d(N_(REGb)+1), . . . , d(C×C′−1) may be filled with <NULL>.

Output value: the indexes may be selected and output in the order of therows in the interleaving matrix.

<NULL> may be excluded from the outputs.

As described above, one CCE may be constituted of the REG bundle indexset after interleaving. That is, CCE j may be constituted of the REGbundle f(6j/L), f(6j/L+1), . . . , f(6j/L+6/L−1), and f(⋅) maycorrespond to the interleaver function.

Meanwhile, the BS may provide the UE with the configuration information(e.g., Y) related to the above-described interleaving via higher layersignaling, e.g., RRC signaling. After receiving the interleaving-relatedconfiguration information from the base station, the UE may appreciatethe interleaving scheme of the control region according to the settingand may blind-decode the download control region in the control regionafter assuming the interleaving scheme.

Embodiment 1-3

According to embodiment 1-3 of the disclosure, there is provided amethod for performing interleaving on the distributed PDCCH, in whichafter interleaving, an offset of a particular size (e.g., Z) may beadditionally applied.

FIG. 8 is a view illustrating an interleaving scheme according toembodiment 1-3 of the disclosure.

Referring to FIG. 8 , the overall control region 800 (e.g., a CORESET)includes a total of 18 REG bundles 801, and each of CCE #0 (802) and CCE#1 (803) consists of two REG bundles 801, for example. The REG bundle(801) index may be input to the interleaving (805) function, and afterinterleaving, may be output. The output REG bundle index, afterinterleaving, may be input to the offset (806) function, and may beindex-offset by a particular value and then output. Here, the offsetvalue Z (804) may be set in various manners. Offsetting may follow,e.g., Equation 2 below.d″(n)=d′(n)+Z mod N _(REGb)  Equation 2

In Equation 2 above, d′(n) may correspond to the nth REG bundle indexafter interleaving, d″(n) may correspond to the nth REG bundle indexafter being offset, Z may correspond to the offset value, and N_(REGb)may correspond to the total number of the REG bundles in the controlregion. In Equation 2 above, “X mod Y” is the operator to output theremainder after X is divided by Y.

Here, Z may be set for the UE by the BS or may be defined as a valuefixed in the system parameter. Where Z is set, the Z value may beprovided from the BS to the UE via higher layer signaling, e.g., RRCsignaling.

As described above, one CCE may be constituted of the REG bundle indexset after interleaving. That is, CCE J may be constituted of the REGbundle (f(6j/L), f(6j/L+1), . . . f(6/L+6/L−1), and f(⋅) may correspondto the interleaver function considering both the interleaver functionand the offset function.

According to embodiment 1-3 of the disclosure, where the control regionsconfigured with different REG bundle sizes overlap each other via theoffset value Z, such a control may be performed that only particularPDCCH candidates cause blocking. The BS may set, for the UE, the offsetvalue Z to minimize the blocking probability based on the circumstancewhere the control regions overlap.

One or more operations among embodiments 1-1, 1-2, and 1-3 describedabove may be operated in combination.

Meanwhile, the BS may provide the UE with the configuration information(e.g., Z) related to the above-described interleaving via higher layersignaling, e.g., RRC signaling. After receiving the interleaving-relatedconfiguration information from the base station, the UE may appreciatethe interleaving scheme of the control region according to the settingand may blind-decode the download control region in the control regionafter assuming the interleaving scheme.

Embodiment 1-4

According to embodiment 1-4 of the disclosure, there is proposed amethod for randomizing interference (e.g., inter-cell interference,inter-TRP interference, or inter-beam interference) among methods forperforming interleaving on the distributed PDCCH.

The REG bundle index input to the interleaver function may follow themethod below.

Input value (d′) offset REG bundle index sequence, i.e., {d′(n), n=0, 1,2, . . . , N_(REGb)}.

In the foregoing, d′(n)=d(n)+W mod N_(REGb). N_(REGb) may correspond tothe total number of the REG bundles in the control region. d(n) maycorrespond to the REG bundle index after offsetting.

In the foregoing, the offset value W may correspond to one of the cellID, TRP ID, synchronization signal block index, component carrier index,or bandwidth part index.

Or, the offset value W may correspond to a value expressed by one ormore functions among the cell ID, TRP ID, synchronization signal blockindex, component carrier index, and bandwidth part index. For example,it may be constituted of a combination of the cell ID and thesynchronization signal block index, e.g., W=cell ID+synchronizationsignal block index.

The offset value W may be set for the UE by the BS via higher layersignaling (e.g., RRC signaling).

Meanwhile, the BS may provide the UE with the configuration information(e.g., W) related to the above-described interleaving via higher layersignaling, e.g., RRC signaling. After receiving the interleaving-relatedconfiguration information from the base station, the UE may appreciatethe interleaving scheme of the control region according to the settingand may blind-decode the download control region in the control regionafter assuming the interleaving scheme.

Embodiment 1-5

According to embodiment 1-5 of the disclosure, there is provided amethod for performing interleaving on the distributed PDCCH, in whichthe BS may set, for the UE, whether to perform additional randomization(or permutation) on the column components of the interleaving matrix (orwhether to perform inter-column permutation, refer to Tables 6 and 7).The configuration information may be set for the UE by the BS via higherlayer signaling (e.g., RRC signaling). As an example, it may be includedas part of the configuration parameters of the control region and beindicated to the UE.

A specific example of embodiment 1-5 of the disclosure is described indetail with reference to interleaving method 4.

[Interleaving Method 5]

Input value: REG bundle index sequence={d(n), n=0, 1, 2, . . . ,N_(REGb)−1},

N_(REGb) may correspond to the total number of the REG bundles in thecontrol region. d(n) may correspond to the nth REG bundle index.

Interleaving matrix generation: generates a matrix of C×C′ size asfollows.

$\begin{bmatrix}{d\left( {P(0)} \right)} & {d\left( {P(1)} \right)} & {d\left( {P(2)} \right)} & \cdots & {d\left( {P\left( {C^{\prime} - 1} \right)} \right)} \\{d\left( {{P(0)} + C^{\prime}} \right)} & {d\left( {{P(1)} + C^{\prime}} \right)} & {d\left( {{P(2)} + C^{\prime}} \right)} & \cdots & {d\left( {{P\left( {C^{\prime} - 1} \right)} + C^{\prime}} \right)} \\ \vdots & \vdots & \vdots & \ddots & \vdots \\{d\left( {{P(0)} + {C^{\prime} \times \left( {C^{\prime} - 1} \right)}} \right)} & {d\left( {{P(1)} + {C^{\prime} \times \left( {C^{\prime} - 1} \right)}} \right)} & {d\left( {{P(2)} + {C^{\prime} \times \left( {C^{\prime} - 1} \right)}} \right)} & \cdots & {d\left( {{P\left( {C^{\prime} + 1} \right)} + {C^{\prime} \times \left( {C^{\prime} - 1} \right)}} \right)}\end{bmatrix}$

C′ may be a value settable by the BS or may correspond to a value fixedin the system parameter. In the foregoing, C=ceil(N_(REGb)/C′). ceil(x)is the function to output the smallest integer among x or largernumbers. Where C×C′>N_(REGb), d(N_(REGb)), d(N_(REGb)+1), . . . ,d(C×C′−1) may be filled with <NULL>.

Here, P(⋅) is any interleaver function.

Where such a setting is made as to perform additional permutation on thecolumn components of the interleaving matrix, it may be any interleaverfunction that meets P(j)=k. Where C′=32, i.e., the output values forP(0), P(1), . . . P(31) may be as follows as an example. Alternatively,the output values may have different patterns or values.

<1, 17, 9, 25, 5, 21, 13, 29, 3, 19, 11, 27, 7, 23, 15, 31, 0, 16, 8,24, 4, 20, 12, 28, 2, 18, 10, 26, 6, 22, 14, 30>

The interleaver function P(⋅) may be defined as a function of systemparameters, and it may have the property of being randomized by afunction induced by the cell ID or RNTI.

Where the setting is made to perform no additional permutation on thecolumn components of the interleaving matrix, the interleaver functionmay be defined as P(j)=j.

Output value: the indexes may be selected and output in the order of therows in the interleaving matrix.

<NULL> may be excluded from the outputs.

Meanwhile, the BS may provide the UE with the configuration information(e.g., whether to perform inter-column permutation) related to theabove-described interleaving via higher layer signaling, e.g., RRCsignaling. After receiving the interleaving-related configurationinformation from the base station, the UE may appreciate theinterleaving scheme of the control region according to the setting andmay blind-decode the download control region in the control region afterassuming the interleaving scheme.

In the first embodiment of the disclosure, the interleaving methodassumes the block interleaver and that, after a particular sequence isinput in the order of the rows of the block interleaver, the output ismade in the order of the columns. The same method may be performed inthe column-row order. For example, after the inputs are made in theorder of columns, the outputs may be made in the order of rows. In thiscase, the parameters for the rows may be replaced with the parametersfor the columns, and the parameters for the columns may be replaced withthe parameters for the rows. The operations may be interpreted in thesame manner.

Second Embodiment

According to the second embodiment of the disclosure, a search space forthe 5G download control channel is proposed. Minimizing powerconsumption due to the UE's blind decoding is very critical in designingthe search space of the 5G download control channel. To that end, uponblind decoding each control channel candidate, it may be considered toreuse the channel estimation value used for prior decoding. For thatpurpose, the search space may be designed so that a higher aggregationlevel of search space is constituted of a set of lower aggregationlevels, for example. Such search space structure may be called a nestedstructure.

According to the disclosure, there is proposed designing a search spaceconsidering the nested structure. According to the disclosure, the wholesearch space may be constituted of multiple partial search spaces, andeach partial search space may meet the above-described nested structure.Each partial search space may be constituted of the same number (orsimilar numbers, as possible) of PDCCH candidates.

The structure proposed herein may ensure the nested structure in eachpartial search space, guaranteeing reduced power consumption in the UEupon blind decoding. The proposed structure may ensure an evenperformance for each partial search space when adjusting the number oftimes of blind decoding with a scaling factor. Adjusting the number oftimes of blind decoding with the scaling factor may correspond to theoperation of, when the number of the PDCCH candidates constituting thewhole search space is X, setting or indicating scaling factor α (0≤α≤1),thereby monitoring the search space constituted of the PDCCH candidatecorresponding to Y=α·X.

FIG. 9 is a view illustrating a search space of a 5G download controlchannel according to embodiment 2 of the disclosure.

Referring to FIG. 9 , an example of a search space 900 constituted of aset of PDCCH candidates 909 in each aggregation level 904, 905, 906, or907. Reference number 908 represents an example of a CCE. One searchspace 900 may include one or more partial search spaces 901 and 902. Inthis case, the number of PDCCH candidates 909 at each aggregation levelin each partial search space may be the same. For example, the wholesearch space may consist of partial search space X and partial searchspace Y, partial search spaces X and Y, each, may be constituted of atotal of N PDCCH candidates, and the whole search space may beconstituted of a total of 2N PDCCH candidates.

For example, according to the second embodiment of the disclosure, thesearch space may be defined as follows.

The nth partial search space may be expressed as follows.S _(k) ^((L))(n)=f(Y _(k)(n),N _(CCE,k)(n)N _(cand) ^((L)),L,x)  Equation 3

In Equation 3, f(⋅) means any function. For example, it may be obtainedfrom Equation 4 below.f=L{(Y _(K) +m′)mod └N _(CCE,k) /L┘}+ii=0,1, . . . ,L−1m=0,1, . . . ,N _(cand) ^((L))−1m′=m+N _(cand) ^((L)·x)   Equation 4

The CCE index set following A) may constitute the search space. S_(k)^((L)) may be defined as the search space corresponding to aggregationlevel (AL)=L in the kth slot, i.e., a set of PDCCH candidates. Y_(k), aparameter for determining the search space in the kth slot, may bedefined as Y_(k)=f(Y_(k-1),A,D). Here, A and D are any constants, andY⁻¹ may be a pre-defined, fixed value, may be set by the base station,or may be defined as, e.g., the UE ID or group ID. N_(CCE,k) may meanthe number of CCEs present in the control region in the kth slot. Lmeans the AL, and N_(cand) ^((L)) may mean the number of PDCCHcandidates corresponding to AL=L. x may mean other system parameters todetermine other search spaces. They may be, e.g., the cell ID,synchronization signal block index, component carrier index, andbandwidth part index. In the foregoing, it may be the same regardless ofthe partial search space index.

As per Equation 2 above, each partial search space may independently beconfigured while they have the same number of PDCCH candidates.

Or, the nth partial search space may be constituted of a set of CCEindexes that are offset by a particular value from those of the 0thpartial search space. That is, it may be represented in Equation 5below.S _(k) ^((L))(n)=S _(k) ^((L))(0)+Δ(n)mod N _(CCE,k)  Equation 5

In Equation 5, Δ(n) may be the CCE index offset value or a value fixedin the system parameter or may be set for the UE by the BS via higherlayer signaling (e.g., RRC signaling).

The above-described whole search space constituted of N partial searchspaces may be expressed as shown in Equation 6 below.

$\begin{matrix}{S_{k}^{(L)} = {\overset{N}{\bigcup\limits_{n = 1}}{S_{k}^{(L)}(n)}}} & {{Equation}6}\end{matrix}$

In the method for determining the number of PDCCH candidates, the numberof PDCCH candidates at each AL=L may be 2 raised to the power of aparticular number, e.g., 2^(j(L)). Here, j(L) may be a natural numberequal or larger than 0. This may be represented as shown in Table 8.

TABLE 8 AL = 1 AL = 2 AL = 4 AL = 8 2^(j(1)) 2^(j(2)) 2^(j(4)) 2^(j(8))

FIG. 9 illustrates an example in which the whole search space 900consists of two partial search spaces, e.g., partial search space #1 901and partial search space #2 902. In the example of FIG. 9 , partialsearch space #1 901 and partial search space #2 902 both may have thesame number of PDCCH candidates, following Table 9 below.

TABLE 9 AL = 1 (907) AL = 2 (906) AL = 4 (905) AL = 8 (904) sum 4 2 1 18

Accordingly, the number of PDCCH candidates constituting the wholesearch space 900 may follow Table 10 below.

TABLE 10 AL = 1 (907) AL = 2 (906) AL = 4 (905) AL = 8 (904) sum 8 4 2 216

The BS may configure a search space agreed on with the UE by theabove-described methods and may transmit the download controlinformation for the UE in a particular PDCCH candidate in the searchspace. The UE may recognize its search space by the above-describedmethods, may perform blind decoding on the PDCCH candidates in thesearch space, and may receive the download control information from theBS based thereupon.

Embodiment 2-1

According to embodiment 2-1 of the disclosure, there is proposeddesigning a search space considering the nested structure.

According to the disclosure, the search space of a particularaggregation level (AL) may be constituted of CCEs present in a set ofCCEs constituting the search space of a reference aggregation level. Inother words, where the CCE set constituting the search space of thereference aggregation level is A, and the search space of the particularaggregation level is B, search space BB may be determined to meet B⊂A.

At this time, the reference aggregation level may be determined by thefollowing methods.

[Method 1]

The reference aggregation level may be the highest aggregation level.For example, assuming that supportable aggregation levels are {1, 2, 4,8}, the highest aggregation level, 8, may be the reference aggregationlevel, and the search spaces of the aggregation levels {1, 2, 4} may beconfigured to be partial sets of the search space of aggregation level8.

[Method 2]

The reference aggregation level may be the highest one of aggregationlevels set for the UE. For example, where supportable aggregation levelsare {1, 2, 4, 8}, and the BS sets the UE to monitor the aggregationlevels {1, 2, 4}, the reference aggregation level may be 4 which is thehighest one of the set aggregation levels. Accordingly, the searchspaces of aggregation levels {1, 2} may be configured to be partial setsof the search space of aggregation level 4.

[Method 3]

The reference aggregation level may be set for the UE by the basestation. For example, where supportable aggregation levels are {1, 2, 4,8}, and the BS sets the UE to monitor the aggregation levels {1, 2, 4},the BS may set, for the UE, 8 as the reference aggregation level. Inthis case, the search spaces of aggregation levels {1, 2, 4} may beconfigured to be partial sets of the search space of aggregation level8. At this time, the UE may not monitor the search space of aggregationlevel 8 and may only use it for the purpose of configuring the searchspaces of aggregation levels {1, 2, 4}.

Third Embodiment

According to the third embodiment of the disclosure, there is proposed amethod for determining the initial sequence value of the DMRStransmitted to decode the PDCCH.

The RS sequence available for the DMRS of the PDCCH may be defined asfollows, for example.

$\begin{matrix}{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}} & {{Equation}7}\end{matrix}$

In Equation 7, r(m) is the signal modulated by quadrature phase shiftkeying (QPSK), c(m) is the binary pseudo-random sequence, and m is theindex. The initial sequence used to generate pseudo-random sequence cmay be defined as follows.c _(init)=)└n _(s)/2┘+1)·(2n _(ID) ^(PDCCH)+1)·2^(c) +b  Equation 8

For the common search space present in the control region set by theMIB, n_(ID) ^(PDCCH) in Equation 8 may be determined based on aparameter, such as cell ID, TRP ID, or synchronization signal blockindex, or based on a value configured by combining the parameters.

For the common search space present in the control region set by theRRC, n_(ID) ^(PDCCH) in Equation 8 may be determined based on aparameter, such as cell ID, TRP ID, or synchronization signal blockindex, component carrier index, or bandwidth part index, or based on avalue configured by combining the parameters.

For the UE-specific search space present in the control region set bythe RRC, n_(ID) ^(PDCCH) in Equation 8 may be determined based on aparameter, such as cell ID, TRP ID, or synchronization signal blockindex, component carrier index, bandwidth part index, UE ID, or virtualcell ID set with the RRC by the BS or based on a value configured bycombining the parameters.

The BS may determine the PDCCH DMRS initial sequence agreed on with theUE as per the above-described methods and may transmit the DMRS in thesequence. The UE may determine the PDCCH DMRS initial sequence agreed onwith the BS by the above-described methods, receive the DMRS assumingthe sequence, and perform channel estimation.

FIGS. 10 and 11 illustrate transmitters, receivers, and processors of aUE and a BS available to perform the above-described embodiments of thedisclosure. FIGS. 10 and 11 illustrate the structure of the BS and UE toperform the interleaving method in the 5G communication system, methodfor setting parameters related to interleaving, method for configuringthe search space, and method for determining the sequence for the PDCCHDMRS. To perform the methods, the transmitters, receivers, andprocessors of the BS and the UE may be operated as per the embodiments.

FIG. 10 is a block diagram illustrating a configuration of a UEaccording to an embodiment of the disclosure.

Referring to FIG. 10 , according to the disclosure, the UE 1000 mayinclude a UE processor 1001, a UE receiver 1002, and a UE transmitter1003. The UE 1000 may add other elements. As necessary or optionally,any one or more of the UE processor 1001, the UE receiver 1002, and theUE transmitter 1003 may be omitted.

The UE processor 1001 may control a series of operations of the UE 1000as per the above-described embodiments. For example, according to anembodiment, the UE processor 1001 may differently control the operationsas per the interleaving method, the method for setting theinterleaving-related parameters, the search space configuring method,and the method for determining the sequence for the PDCCH DMRS.Meanwhile, as an example, the UE processor 1001 may include at least oneprocessor (e.g., a CPU or a graphics processing unit (GPU) or both). TheUE receiver 1002 and the UE transmitter 1003 may collectively bereferred to as a transceiver (or communication interface) according toan embodiment. The transceiver may transmit or receive signals to/fromthe base station. The signals may include control information and data.To that end, the transceiver may include a radio frequency (RF)transmitter for frequency-up converting and amplifying signalstransmitted and an RF receiver for low-noise amplifying signals receivedand frequency-down converting the frequency of the received signals. Thetransceiver may receive signals via a radio channel, output the signalsto the UE processor 1001, and transmit signals output from the UEprocessor 1001 via a radio channel. Meanwhile, the UE processor 1001 maycontrol the operations of the UE according to a combination of at leastone or two or more of the above-described first to third embodiments ofthe disclosure.

The UE 1000 may further include a storage unit configured to store abasic program for operating the UE 1000, application programs, controlinformation or other data. Further, the storage unit may include atleast one storage medium of a flash memory-type, hard disk-type,multimedia card-type, a micro card-type, or other-type memory (e.g., asecure digital (SD) or an extreme digital (xD) memory), a magneticmemory, a magnetic disk, an optical disc, a random access memory (RAM),a static RAM (SRAM), a read only memory (ROM), a programmable ROM(PROM), or an electrically erasable PROM (EEPROM). The UE processor 1001may perform various operations using various programs, contents, or datastored in the storage unit.

FIG. 11 is a block diagram illustrating a configuration of a BSaccording to an embodiment of the disclosure.

Referring to FIG. 11 , according to the disclosure, the BS 1100 mayinclude a base station processor 1101, a base station receiver 1102, anda base station transmitter 1103. The BS 1100 may add other elements. Asnecessary or optionally, any one or more of the BS processor 1101, theBS receiver 1102, and the BS transmitter 1103 may be omitted.

The BS processor 1101 may control a series of operations of the basestation 1100 as per the above-described embodiments. For example,according to an embodiment, the UE processor 1001 may differentlycontrol the operations as per the interleaving method, the method forsetting the interleaving-related parameters, the search spaceconfiguring method, and the method for determining the sequence for thePDCCH DMRS. As necessary, the BS processor 1101 may perform control totransmit various additional indicators and configuration information.Meanwhile, as an example, the BS processor 1101 may include at least oneprocessor (e.g., a CPU or a graphics processing unit (GPU) or both). TheBS receiver 1102 and the BS transmitter 1103 may collectively bereferred to as a transceiver (or communication interface) according toan embodiment. The transceiver may transmit or receive signals to/fromthe UE. The signals may include control information and data. To thatend, the transceiver may include a radio frequency (RF) transmitter forfrequency-up converting and amplifying signals transmitted and an RFreceiver for low-noise amplifying signals received and frequency-downconverting the frequency of the received signals. The transceiver mayreceive signals via a radio channel, output the signals to the BSprocessor 1101, and transmit signals output from the BS processor 1101via a radio channel. Meanwhile, the BS processor 1101 may control theoperations of the BS according to a combination of at least one or twoor more of the above-described first to third embodiments of thedisclosure.

The BS 1100 may further include a storage unit configured to store abasic program for operating the BS 1100, application programs, controlinformation or other data. The BS processor 1101 may perform variousoperations using various programs, contents, or data stored in thestorage unit.

The embodiments herein are provided merely for better understanding ofthe disclosure, and the disclosure should not be limited thereto orthereby. In other words, it is apparent to one of ordinary skill in theart that various changes may be made thereto without departing from thescope of the disclosure. Further, the embodiments may be practiced incombination. For example, the first, second, and third embodiments ofthe disclosure may partially be combined and be operated by the BS andthe UE. Although the embodiments are proposed in association with newradio (NR) systems, various modifications thereto may apply to othervarious systems, such as frequency division duplex (FDD) or timedivision duplex (TDD) LTE systems.

Although preferred embodiments of the disclosure have been shown anddescribed in connection with the drawings and particular terms have beenused, this is to provide a better understanding of the disclosure and isnot intended to limit the scope of the disclosure. It is apparent to oneof ordinary skill in the art that various changes may be made theretowithout departing from the scope of the disclosure.

The above-described operations may be realized by equipping a memorydevice retaining their corresponding codes in any component of theserver or terminal device of the communication system. That is, theprocessor in the BS or UE may execute the above-described operations byreading and running the program codes stored in the memory device by aprocessor or CPU.

As described herein, various components or modules in the server orterminal device may be operated using a hardware circuit, e.g., acomplementary metal oxide semiconductor-based logic circuit, firmware,software, and/or using a hardware circuit such as a combination ofhardware, firmware, and/or software embedded in a machine-readablemedium. As an example, various electric structures and methods may beexecuted using electric circuits such as transistors, logic gates, orASICs.

Although specific embodiments of the disclosure have been describedabove, various changes may be made thereto without departing from thescope of the disclosure. Thus, the scope of the disclosure should not belimited to the above-described embodiments, and should rather be definedby the following claims and equivalents thereof.

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

What is claimed is:
 1. A method performed by a terminal in a wirelesscommunication system, the method comprising: transmitting, from a basestation, a configuration of a reference aggregation level; identifying asearch space set, for the terminal, including a plurality of sub-searchspaces, wherein an aggregation level search space of a sub-search spaceis a subset of a reference aggregation level search space of thesub-search space, and a number of physical downlink control channel(PDCCH) candidates for each of the plurality of sub-search spaces is thesame; and receiving, from the base station, downlink control informationby monitoring a PDCCH candidate of the search space set, wherein theaggregation level search space is set to be monitored for the downlinkcontrol information and the reference aggregation level search space isnot monitored for the downlink control information.
 2. The method ofclaim 1, further comprising: receiving, from the base station,information configuring a scaling factor associated with a blinddecoding number, wherein a number of the PDCCH candidates monitored forthe downlink control information is identified by multiplying thescaling factor with a total number of PDCCH candidates of the searchspace set.
 3. The method of claim 1, wherein a number of PDCCHcandidates for each aggregation levels is same for the plurality ofsub-search spaces, and wherein the number of PDCCH candidates for eachaggregation level is a power of
 2. 4. The method of claim 1, wherein acontrol channel element (CCE) index offset between a first sub-searchspace and a second sub-search space is configured by a higher layersignaling from the base station.
 5. The method of claim 1, wherein aspecific aggregation level search space consists of at least one controlchannel element (CCE) of a CCE set for the reference aggregation levelsearch space, and wherein, in case that supportable aggregation levelsare {1,2,4,8}, aggregation levels to be monitored are {1,2,4}, and thereference aggregation level configured by the base station is {8}, anaggregation level {8} search space is used to configure aggregationlevel {1, 2, 4} search spaces and is not monitored for the downlinkcontrol information.
 6. A method performed by a base station in awireless communication system, the method comprising: transmitting, to aterminal, a configuration of a reference aggregation level; identifyinga search space set, for the terminal, including a plurality ofsub-search spaces, wherein an aggregation level search space of asub-search space is a subset of a reference aggregation level searchspace of the sub-search space, and a number of physical downlink controlchannel (PDCCH) candidates for each of the plurality of sub-searchspaces is the same; and transmitting, to the terminal, downlink controlinformation on a PDCCH candidate of the search space set, wherein theaggregation level search space is set to be monitored for the downlinkcontrol information and the reference aggregation level search space isnot monitored for the downlink control information.
 7. The method ofclaim 6, further comprising: transmitting, to the terminal, informationconfiguring a scaling factor associated with a blind decoding number,wherein a number of the PDCCH candidates monitored for the downlinkcontrol information is identified by multiplying the scaling factor witha total number of PDCCH candidates of the search space set.
 8. Themethod of claim 6, wherein a number of PDCCH candidates for eachaggregation levels is same for the plurality of sub-search spaces, andwherein the number of PDCCH candidates for each aggregation level is apower of
 2. 9. The method of claim 6, wherein a control channel element(CCE) index offset between a first sub-search space and a secondsub-search space is configured by a higher layer signaling to theterminal.
 10. The method of claim 6, wherein a specific aggregationlevel search space consists of at least one control channel element(CCE) of a CCE set for the reference aggregation level search space, andwherein, in case that supportable aggregation levels are {1,2,4,8},aggregation levels to be monitored are {1,2,4}, and the referenceaggregation level configured by the base station is {8}, an aggregationlevel {8} search space is used to configured aggregation level {1,2,4}search spaces and is not monitored for the downlink control information.11. A terminal in a wireless communication system, the terminalcomprising: a transceiver configured to transmit and receive a signal;and a controller configured to: receive, from a base station, aconfiguration of a reference aggregation level, identify a search spaceset, for the terminal, including a plurality of sub-search spaces,wherein an aggregation level search space of a sub-search space is asubset of a reference aggregation level search space of the sub-searchspace, and a number of physical downlink control channel (PDCCH)candidates for each of the plurality of sub-search spaces is the same,and receive, from the base station, downlink control information bymonitoring a PDCCH candidate of the search space set, wherein theaggregation level search space is set to be monitored for the downlinkcontrol information and the reference aggregation level search space isnot monitored for the downlink control information.
 12. The terminal ofclaim 11, wherein the controller is further configured to receive, fromthe base station, information configuring a scaling factor associatedwith a blind decoding number, and wherein a number of the PDCCHcandidates monitored for the downlink control information is identifiedby multiplying the scaling factor with a total number of PDCCHcandidates of the search space set.
 13. The terminal of claim 11,wherein a number of PDCCH candidates for each aggregation levels is samefor the plurality of sub-search spaces, and wherein the number of PDCCHcandidates for each aggregation level is a power of
 2. 14. The terminalof claim 11, wherein a control channel element (CCE) index offsetbetween a first sub-search space and a second sub-search space isconfigured by a higher layer signaling from the base station.
 15. Theterminal of claim 11, wherein a specific aggregation level search spaceconsists of at least one control channel element (CCE) a CCE set for thereference aggregation level search space, and wherein, in case thatsupportable aggregation levels are {1,2,4,8}, aggregation levels to bemonitored are {1,2,4}, and the reference aggregation level configured bythe base station is {8}, an aggregation level {8} search space is usedto configure aggregation level {1, 2, 4} search spaces and is notmonitored for the downlink control information.
 16. A base station in awireless communication system, the base station comprising: atransceiver configured to transmit and receive a signal; and acontroller configured to: transmit, to a terminal, a configuration of areference aggregation level, identify a search space set, for aterminal, including a plurality of sub-search spaces, wherein anaggregation level search space of a sub-search space is a subset of areference aggregation level search space of the sub-search space, and anumber of physical downlink control channel (PDCCH) candidates for theplurality of sub-search spaces is the same, and transmit, to theterminal, downlink control information on a PDCCH candidate of thesearch space set, wherein the aggregation level search space is set tobe monitored for the downlink control information and the referenceaggregation level search space is not monitored for the downlink controlinformation.
 17. The base station of claim 16, wherein the controller isfurther configured to transmit, to the terminal, information configuringa scaling factor associated with a blind decoding number, and wherein anumber of the PDCCH candidates monitored for the downlink controlinformation is identified by multiplying the scaling factor with a totalnumber of PDCCH candidates of the search space set.
 18. The base stationof claim 16, wherein a number of PDCCH candidates for each aggregationlevels is same for the plurality of sub-search spaces, and wherein thenumber of PDCCH candidates for each aggregation level is a power of 2.19. The base station of claim 16, wherein a control channel element(CCE) index offset between a first sub-search space and a secondsub-search space is configured by a higher layer signaling to theterminal.
 20. The base station of claim 16, wherein a specificaggregation level search space consists of at least one control channelelement (CCE) of a CCE set for the reference aggregation level searchspace, and wherein, in case that supportable aggregation levels are{1,2,4,8}, aggregation levels to be monitored are {1,2,4}, and thereference aggregation level configured by the base station is {8}, anaggregation level {8} search space is used to configured aggregationlevel {1,2,4} search spaces and is not monitored for the downlinkcontrol information.